1. Field of the Invention
The present invention relates to novel derivatives of .alpha.-(4-substituted phenyl)ethyl alcohols and liquid crystal compositions containing at least one of said derivatives.
2. Description of the Prior Art
Presently, liquid crystal display devices predominantly utilize the nematic phase of liquid crystals, while active research has also been conducted in recent years on various display modes utilizing smectic phases. Liquid crystal display which utilizes a ferroelectric liquid crystal exhibiting chiral smectic C phase is expected to be especially promising because it is adapted to high-capacity display and has wide viewing angles.
The above-mentioned ferroelectric liquid crystals are first required to exhibit chiral smectic C phase in the wide range of temperatures at around room temperature. In order to realize high-capacity displays, they are also required to have high-speed responsibility as a device characteristic. Thus, ferroelectric liquid crystals are required to have higher spontaneous polarization and lower viscosity. In addition, in order to show good orientation and bistability in a liquid crystal cell, they are required to exhibit a phase sequence of I.NAC (Isotropic-Nematic-Smectic-A-Smectic C) or IAC (Isotropic-Smectic-A-Smectic C), and to have sufficient longer helical pitch in nematic and smectic C phase.
At the present time, there is no single liquid crystal compound which satisfies all requirements mentioned above and therefore ferroelectric liquid crystal mixtures are usually prepared by adding an optically active compound to a liquid crystal composition or compound with low viscosity. But because such liquid crystal composition with good quality should satisfy various requirements as mentioned above, the compositions are sometimes necessary to be prepared by mixing a compound such as an optically active one other than liquid crystalline compounds.
The requirements other than the high-speed responsibility of the above-mentioned conditions have been satisfied by conventional mixing techniques, but the high-speed responsibility have not been sufficiently obtained yet.
Accordingly, it has been also desired to develop new optically active compounds which can induce greater spontaneous polarization in liquid crystal compositions to realize the high-speed responsibility.
Recently, such compounds as unsubstituted .alpha.-phenylethyl 4'-alkoxybiphenyl-4-carboxylates have been reported as an optically active compound used by adding to liquid crystal compositions (Japanese Published Unexamined Patent Application No. 583/1987, published on 6th Jan., 1987).